1. Field of the Invention
The present invention relates to a scintillator panel for use in a medical diagnostic apparatus, a non-destruction inspection apparatus, or the like, a radiation detection device, a method of producing the radiation detection device, and a radiographic system. In particular, the present invention relates to a scintillator panel, a radiation detection device, and a radiation image pick-up system for use in X-ray photography. It is to be noted that, in this invention, the radiation includes electromagnetic waves such as X-rays, γ-rays, and so forth.
2. Description of the Related Art
In general, X-ray film systems comprise a fluorescent screen containing an X-ray scintillator layer therein and a two-sided coating material. In recent years, digital radiation-detection apparatuses, containing an X-ray scintillator layer and a two-dimensional photodetector, respectively, have been intensively investigated and developed. The image characteristics of such digital radiation-detection apparatus are high, and the image data, which is digital, can be transferred to and stored on network computer systems for common use. Thus, various patent applications have been filed.
For example, Japanese Patent Laid-Open Nos. 2000-9845 and 9-145845 describe radiation detection devices with increased sensitivity and sharpness. In these apparatuses, a supporting plate having a scintillator layer for converting radiation to light-beams detectable by photoelectric conversion elements is bonded to a photodetector which contains a photoelectric conversion element portion, the photoelectric conversion element portion having electrical elements such as a plurality of photosensors, TFTs (thin film transistor) and the like arranged in a two-dimensional pattern. Moreover, in the radiation detection device disclosed in Japanese Patent Laid-Open No. 2000-284053, a scintillator layer for converting radiation to light-beams detectable by photoelectric conversion elements is formed directly on a photodetector, the photodetector containing a photoelectric conversion element portion in which a plurality of photosensors and electrical elements such as TFTs or the like are provided in a two-dimensional arrangement.
FIG. 9 is a cross-sectional view showing a known radiation detection device. In FIG. 9, a sensor panel 100 is shown which comprises a glass substrate 101, a photoelectric conversion element portion 102 comprising photosensors using amorphous silicon and TFTs, a wiring 103, an electrode lead-out portion (electrode pad) 104, and a protection layer 105 made of silicon nitride or the like. Moreover, a scintillator panel (also called a scintillator panel) 110 is bonded to the sensor panel 100 by means of an adhesive or a tacky-adhesive. The scintillator panel 110 comprises a scintillator supporting plate 111 and a scintillator layer 112, which are formed so as to correspond to the photoelectric conversion element portion 102. An anisotropic conductive adhesive 3 is formed on a terminal 2a of a flexible circuit board 2 having a detection integrated circuit IC (not shown) mounted thereon. The electrode lead-out portion 104 and the sensor panel 100 are bonded to each other via the adhesive by heating and pressing. The upper side of the electrode lead-out portion 104, located between the end (connection portion) of the terminal 2a and the end of the scintillator panel 110 is sealed with a sealer (sealing resin) 1.
In the above-described known examples, the terminal 2a of the flexible circuit board 2 is bonded to the electrode lead-out portion 104 via the anisotropic conductive adhesive 3 provided on the terminal 2a in advance, by heating and pressing, as shown in FIG. 9. The anisotropic conductive adhesive 3 provided on the terminal 2a is arranged slightly on the inner side of the end of the terminal 2a, so that the adhesive is prevented from being forced out from the end of the terminal 2a when the terminal 2a and the electrode lead-out portion 104 are bonded to each other by heating and pressing (see FIG. 9).
According to the known examples, sealing resin can be applied to the upper side of the terminal 2a to seal the terminal 2a of the flexible circuit board 2. In this case, it is difficult for the resin to flow into the stepped portion defined by the anisotropic conductive adhesive 3 and the underside of the end of the terminal 2a called the gap. Thus, in some cases, a pore 11 is formed (see FIG. 9).
Undesirably, water may permeate through the resin layer into the pore 11 (space) and contact with a wiring, thus forming a water layer. The water layer dissolves corrosive substances such as chlorides or the like, which in turn corrodes the wiring peeled and exposed on the electrode lead-out portion 104. Accordingly, in the case in which the pore 11 is formed in the gap, the sealing process must be continued until the resin flows into the gap so that the pore is eliminated, or a further resin is required to flow into the gap so that the pore is eliminated. Thus, problems occur in that it takes extra time to perform the sealing process.
On the other hand, in the case in which the pore 11 is not formed in the gap, a sealer (sealing resin) 1 is formed on the scintillator panel 110, so that water can be prevented from invading the scintillator panel 110 via the end thereof. The scintillator panel (or scintillator panel) 110 is reinforced, and the scintillator layer 112 can be prevented from peeling off from the sensor panel 100, the scintillator supporting plate 111, and so forth. In the case in which the scintillator layer 112 is formed of scintillator grains, 50% to 70% of the scintillator grains have a grain size of about 5 μm to 50 μm, 1% to 10% of a resin acts as a binder for the scintillator grains, and pores between the grains are contained in the scintillator layer 112. In the scintillator layer 112, pores present between the scintillator grains are not filled with the binder resin, so that light-rays emitted from the scintillator by the X-ray irradiation can be guided to the photoelectric conversion elements as efficiently as possible, thus obtaining high characteristics.
Conventionally, when the sealer 1 is applied to the end of the scintillator panel 110, the sealer 1 sinks into the pores between the grains of the scintillator layer 112 (see a sinking portion 10 shown in FIG. 9). In this case, the resin sinks into the scintillator layer 112 fills the pores of the scintillator layer 112. Thus, in X-ray photography, light-rays emitted from the scintillator grains are absorbed by the resin filling the pores. A region with different refractive indexes is formed, which is caused by the resin filling the pores, disturbing the advancement of light-beams. Thus, in some cases, undesirable image defects are generated, mainly in the end of the scintillator layer 112.
Accordingly, a sealing resin countermeasure region (in the range of at least about 3 mm or 5 mm) is provided on the sensor panel 100 in the outer periphery of the scintillator panel 110. Therefore, even if it is desired to increase a photographic region (pixel region, the pixel region cannot be set to exceed the countermeasure region.
It is an object of the present invention to provide a radiation detection device in which defects in sealing of the end of a scintillator panel and in sealing of the end of a terminal of a flexible circuit board are nearly eliminated, thereby reducing the sealing processing time and increasing a pixel region. Such a radiation device has nearly no image defects, has high image qualities and has a long service life. It is also an object of the present invention to provide a method of producing the radiation detection device.